Air dry vs. kiln dry

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a solar kiln is gentle enough that it just speeds up the process of air drying - forced heat kiln tends to cause more warping just due to the dynamics of the process overall. ( in the case of board lumber and of course adds to the production costs of same, but that becomes a trade off vs the 2 years or so of air drying less of course when using a solar kiln) advantage of forced heat though is killing any bugs so most use a combination of the two. Depending on your local Solar can reach temps of the forced air system but can't maintain it for the prescribed bug killing specs for the most part.
 
Here's a breakdown the way I view it;

Air Drying Lumber;
Advantages-
Minimal cost
If stacked and stickered correctly you should get a predictable product.
Because it dries slowly you get minimal checking.
Working with air dried lumber is easier/more enjoyable. I've read many books by legendary woodworkers who prefer to only work with air dried lumber, I've experienced this also. Air dried lumber just seems to be worked easier, esp with hand tools.
Air dried lumber keeps more of it's beauty (coloring, contrasts, figure).
Disadvantages-
You have to wait for it to dry.
You can't kill any insects/bugs in your wood.
Some pines need high temps to help "set" or 'cure' the resins/pitch in the wood.

Kiln Drying Lumber
Advantages-
You don't have to wait as long.
Kills insects/bugs.
Disadvantages-
Cost
Can get checking if dried too quickly. You can really ruin wood if you don't dry it correctly in a kiln (ie too fast or too high temps)
Lose some color and beauty of the wood.
May lose some workability of the wood.
You still need to air dry to a certain point BEFORE you put it into the kiln.

I've worked almost exclusively with air dried lumber for 25 years, at this point I wouldn't really consider building a kiln. I've got plenty of stock drying and cut more each year. I've also learned a lot, and I've lost some stock, but overall I have had great success with air drying. My patience has yielded many many board feet of quality walnut and cherry to keep me busy at my woodworking hobby.

I think a lot of guys get really worked up over moisture content. I keep an eye on it, but I simply let green wood sit for a few years stacked, stickered and out of the elements. I then rotate that wood into my shop and let it acclimate there for a few months. After that I just use it.

I'm sure I missed some "wisdom" here, but there are many on this site that know more than me. Hopefully we'll hear from them so we can even learn more.
 
Pretty much everything stated in the above post is how I view the two. Love how vibrant the color is with air dried lumber and haven't personally had a problem with bugs or being dry enough to this point. Just be patient.

I've been considering a solar kiln as well because of how cheap it is and speeds up the drying process.
 
Any wisdom on Air dried lumber Vs. Kiln dried lumber? Looking to build a solar kiln, but not sure if I need to.
What will you be using the lumber for? This determines the extent of needed drying.

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Kiln dried all depends on the setup.

The kiln we have keeps the room at around 80* and uses fans and a large dehumidifer. It takes about a month to dry a load.

Some kilns heat go much hotter and take only a few days. Trade off is more cull.
 
Here's a breakdown the way I view it;

Air Drying Lumber;
Advantages-
Minimal cost
If stacked and stickered correctly you should get a predictable product.
Because it dries slowly you get minimal checking.
Working with air dried lumber is easier/more enjoyable. I've read many books by legendary woodworkers who prefer to only work with air dried lumber, I've experienced this also. Air dried lumber just seems to be worked easier, esp with hand tools.
Air dried lumber keeps more of it's beauty (coloring, contrasts, figure).
Disadvantages-
You have to wait for it to dry.
You can't kill any insects/bugs in your wood.
Some pines need high temps to help "set" or 'cure' the resins/pitch in the wood.

Kiln Drying Lumber
Advantages-
You don't have to wait as long.
Kills insects/bugs.
Disadvantages-
Cost
Can get checking if dried too quickly. You can really ruin wood if you don't dry it correctly in a kiln (ie too fast or too high temps)
Lose some color and beauty of the wood.
May lose some workability of the wood.
You still need to air dry to a certain point BEFORE you put it into the kiln.

I've worked almost exclusively with air dried lumber for 25 years, at this point I wouldn't really consider building a kiln. I've got plenty of stock drying and cut more each year. I've also learned a lot, and I've lost some stock, but overall I have had great success with air drying. My patience has yielded many many board feet of quality walnut and cherry to keep me busy at my woodworking hobby.

I think a lot of guys get really worked up over moisture content. I keep an eye on it, but I simply let green wood sit for a few years stacked, stickered and out of the elements. I then rotate that wood into my shop and let it acclimate there for a few months. After that I just use it.

I'm sure I missed some "wisdom" here, but there are many on this site that know more than me. Hopefully we'll hear from them so we can even learn more.

Bmac,
Thanks for the insight. I'm pretty much doing everything you had mentioned. I'm also in no hurry to use the lumber, so air drying is not an issue. With the issues of bugs or fungi. Do you know of any methods of dealing with this with air drying lumber? Is there a way to treat the wood without affecting the finished product?

Thanks
 
Will be using the wood for wood projects, i.e. cabinets, furniture etc.
OK, so yes, the less moisture content the better. Always best to air dry for a few months before a kiln anyways. From that point, a kiln is only worth doing if you'll use all the lumber right away, or you have a low humidity area to store it. No matter how dry you get lumber, if you store it in a non climate controlled area, it will gain moisture. Ideally, for someone in a non production hobby, best bet is just to do like mentioned above. Air stack until a few months before the lumber is needed, then bring into a shop to let it finish. Keep a dehumidifier in there also to control humidity. Then you're good to go!

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To answer your bug question, I remember seeing guys rolling some kind of pesticide on slabs they milled immediately after each cut. This definitely prevents bugs after the wood has been milled, but I'm not sure about th scenario where bugs were already burrowed in the log.

I would assume once a bug tries to burrow after hag stuffs been applied, it would die from eating the pesticide but I honestly have never looked into it.

I think the guy who did it was blaisentrees actually. He's a member here who has a YouTube channel and instagram account. Don't hold me to the spelling of his screenname but maybe he will chime in. Worth looking into if bugs concern you.
 
Bmac,
Thanks for the insight. I'm pretty much doing everything you had mentioned. I'm also in no hurry to use the lumber, so air drying is not an issue. With the issues of bugs or fungi. Do you know of any methods of dealing with this with air drying lumber? Is there a way to treat the wood without affecting the finished product?

Thanks

If you are air drying a few simple steps can help minimize bugs/insects and molds.
First, stack to get good airflow through your drying lumber, this helps dry it better anyway and will discourage mold and other destructive growths on your lumber. Also stack off the ground a good ways for good air flow under the stack. Make sure vegetation does grow up under and around your stack. I spray roundup and weedwack around and under my stacks as needed.

Insects and bugs are a little harder to prevent, and you may not be able to completely prevent them. The wood species you mill makes a big difference here. I've had some bug issues with the following species;
Red Oak, maple, pine.
I've had no issues with the following species;
Cherry, walnut, cedar, and sassafras.
I've had very minor bug issues with white oak but it does much better than red oak.

When I talk about bug issues I'm talking about bug issues within the heartwood. All bark and sapwood is vulnerable to insect problems pretty much regardless of the species. I've milled long dead walnut, sassafras, and cedar where the bark and sapwood is full of insect problems but the heartwood is just fine. I've also found this to be the case sometimes with cherry logs, but sometimes these have turned soft and punky. Just need to check cherry as they turn bad faster than the others I mentioned. If I'm milling dead trees like these then I just harvest the heartwood and try to get all the bark and sapwood off before stacking and stickering. If those same logs are red oak, maple or pine and they already have insect problems I don't even bother to mill it. So if you are milling wood with bug and decay issues already you need to stick with wood that has resistant heartwood and not waste time on the vulnerable species.

Now if you are milling live or freshly cut logs with no major insect problem to begin with then you can likely dry it with the bark on, but being proactive and removing the bark and most of the sapwood is not a bad idea for more vulnerable species.

Finally, getting the wood dry makes the wood much less desirable to insects.

Love to hear other people's experience with this issue.
 
To answer your bug question, I remember seeing guys rolling some kind of pesticide on slabs they milled immediately after each cut. This definitely prevents bugs after the wood has been milled, but I'm not sure about th scenario where bugs were already burrowed in the log.

I would assume once a bug tries to burrow after hag stuffs been applied, it would die from eating the pesticide but I honestly have never looked into it.

I think the guy who did it was blaisentrees actually. He's a member here who has a YouTube channel and instagram account. Don't hold me to the spelling of his screenname but maybe he will chime in. Worth looking into if bugs concern you.

Blaise uses a borax-type solution.
 
Is that a new to you house or a newly built house?

A newly built house is going to have moisture leaving the concrete basement walls for a year or two after it is built.
 
There is huge difference between air dried vs kiln dried lumber. I studied wood technology in college and have a BS in Forestry.
Air dried lumber will never get below the 10-12% moisture content. The cell walls will never be able to seal out moisture and therefore the air dried lumber will change moisture content dependent on the surrounding humidity. The structural strength will never increase.
Kiln dried lumber has a moisture content of about 6%. The cell walls undergo a physical and miner chemical chamge due to the forced heat. This change in the cell wall blocks any future absorption of moisture from surrounding humidity. Also there is a change in the structural properties of the wood giving it better strength.
This is why all commercial lumber is kiln dried.
That said I currently air dry my lumber. I sticker it up in a large shed that has ventilation and let it dry at least 12 months for every inch of thickness. I have a moisture meter to monitor the wood. Every species dries differently so monitoring is important.
I am considering building a solar kiln to get the most of out of the lumber. At the moment I have higher priorities.

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There is huge difference between air dried vs kiln dried lumber. I studied wood technology in college and have a BS in Forestry.
Air dried lumber will never get below the 10-12% moisture content. The cell walls will never be able to seal out moisture and therefore the air dried lumber will change moisture content dependent on the surrounding humidity. The structural strength will never increase.
Kiln dried lumber has a moisture content of about 6%. The cell walls undergo a physical and miner chemical chamge due to the forced heat. This change in the cell wall blocks any future absorption of moisture from surrounding humidity. Also there is a change in the structural properties of the wood giving it better strength.
This is why all commercial lumber is kiln dried.
That said I currently air dry my lumber. I sticker it up in a large shed that has ventilation and let it dry at least 12 months for every inch of thickness. I have a moisture meter to monitor the wood. Every species dries differently so monitoring is important.
I am considering building a solar kiln to get the most of out of the lumber. At the moment I have higher priorities.

Sent from my SAMSUNG-SM-G891A using Tapatalk


I really hate to disagree with you, but everything I've read and studied refutes what you are saying. Now granted I do not have a degree in forestry but this is my understanding;

Wood, whether air dried or kiln dried takes up moisture and eventually equalizes with the environment it is in. I believe this is called the wood's EMC, Equilibrium Moisture Content. I know for air dried in the Mid-Atlantic area of the country my EMC for outside storage is around 12%. That means lumber stored outside will never go below this EMC. But once that wood is moved inside to my shop and I let it acclimate for a few months. It then reaches the EMC for my shop which is about 8-9% (I do not have a completely climate controlled shop). Then I build and bring the product inside where it continues to dry some and eventually reaches the approximate EMC of 6% for a controlled climate like my house.

Kiln dried lumber is dried to 5-6%, but that wood will gain moisture if not stored in an environment that is 6% EMC. So if I bought kiln dried lumber from a lumber yard that was storing it outside, the wood will be wetter than it was once it left the kiln. In fact, if you stored kiln dried lumber outside long enough it would reach the same EMC of air dried lumber stored outside.

From my study there is no process that you can do to wood, whether its kiln drying, a finish or a sealer, that prevents wood from gaining and losing moisture from it's environment.

Now I do agree that kiln dried wood behaves differently, the rapid drying can create built up internal stresses in kiln dried wood. Also I believe that air dried is easier to work with hand tools, easier to bend, and retains more vibrant colors.

This give and take of moisture is why one needs to build with that concept in mind, frame and panel construction is a prime example. You need to build with the idea that the wood is free to move across the grain.

You can also build using moisture content to your advantage. Here is a photo of a chair made from air dried wood, I would have never been able to bend those arms with kiln dried lumber. The process I used for those arms is bent lamination and I used wood that was a little wetter that my 8-9% acclimated wood in my shop. Once bent I let it acclimate and then I shaped it.

Dining Chair 1.JPG

Also, I used wood for the seat that was 11-12%, outside EMC, and used drier wood for the spindles and legs. Now as the wood in the seat dries and shrinks it creates a tighter joint for the legs and the spindles. This concept has been long known by chair makers for centuries and knowing how wood behaves in it's environment, regardless of it being air dried or kiln dried, can mean success or failure with your projects.
 
I really hate to disagree with you, but everything I've read and studied refutes what you are saying. Now granted I do not have a degree in forestry but this is my understanding;

Wood, whether air dried or kiln dried takes up moisture and eventually equalizes with the environment it is in. I believe this is called the wood's EMC, Equilibrium Moisture Content. I know for air dried in the Mid-Atlantic area of the country my EMC for outside storage is around 12%. That means lumber stored outside will never go below this EMC. But once that wood is moved inside to my shop and I let it acclimate for a few months. It then reaches the EMC for my shop which is about 8-9% (I do not have a completely climate controlled shop). Then I build and bring the product inside where it continues to dry some and eventually reaches the approximate EMC of 6% for a controlled climate like my house.

Kiln dried lumber is dried to 5-6%, but that wood will gain moisture if not stored in an environment that is 6% EMC. So if I bought kiln dried lumber from a lumber yard that was storing it outside, the wood will be wetter than it was once it left the kiln. In fact, if you stored kiln dried lumber outside long enough it would reach the same EMC of air dried lumber stored outside.

From my study there is no process that you can do to wood, whether its kiln drying, a finish or a sealer, that prevents wood from gaining and losing moisture from it's environment.

Now I do agree that kiln dried wood behaves differently, the rapid drying can create built up internal stresses in kiln dried wood. Also I believe that air dried is easier to work with hand tools, easier to bend, and retains more vibrant colors.

This give and take of moisture is why one needs to build with that concept in mind, frame and panel construction is a prime example. You need to build with the idea that the wood is free to move across the grain.

You can also build using moisture content to your advantage. Here is a photo of a chair made from air dried wood, I would have never been able to bend those arms with kiln dried lumber. The process I used for those arms is bent lamination and I used wood that was a little wetter that my 8-9% acclimated wood in my shop. Once bent I let it acclimate and then I shaped it.

View attachment 640096

Also, I used wood for the seat that was 11-12%, outside EMC, and used drier wood for the spindles and legs. Now as the wood in the seat dries and shrinks it creates a tighter joint for the legs and the spindles. This concept has been long known by chair makers for centuries and knowing how wood behaves in it's environment, regardless of it being air dried or kiln dried, can mean success or failure with your projects.
There is a cellular change that occurs when kiln drying lumber there by limiting the uptake of moisture. When you spend 4 years getting a degree in wood technology then come back and we can talk. The books you pick up in barnes and nobles are for woodworkers like yourself and do not study the molecular structure of the wood. Go ahead and refute, I have all the books to show otherwise as well as studies and many papers. Typically this is why I never post in these forums because arm chair quarterbacks always know best.


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I apologize if I sound rude, but if the question is asked and a sound scientific answer which is universally accepted throughout academia and industry is given then just accept the answer instead of relying on hogwash from a bookstore.

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There is a cellular change that occurs when kiln drying lumber there by limiting the uptake of moisture. When you spend 4 years getting a degree in wood technology then come back and we can talk. The books you pick up in barnes and nobles are for woodworkers like yourself and do not study the molecular structure of the wood. Go ahead and refute, I have all the books to show otherwise as well as studies and many papers. Typically this is why I never post in these forums because arm chair quarterbacks always know best.


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Well you've already changed your statement. In your first statement you said;
"Kiln dried lumber has a moisture content of about 6%. The cell walls undergo a physical and miner chemical chamge due to the forced heat. This change in the cell wall blocks any future absorption of moisture from surrounding humidity."
In the statement above you say;
"There is a cellular change that occurs when kiln drying lumber there by limiting the uptake of moisture"

So, does kiln drying block or just limit moisture uptake, there is a BIG difference between those two statements. If it just limits moisture uptake than my response to you about EMC was correct, it's just kiln dried takes longer to pick up moisture, but it still picks it up.

So from your first statement I'd love to see the evidence of the following-
-That air dried lumber can never get below 10-12%.
-That that Kiln dried lumber will not increase in moisture content, or MC.

Here is a very sound reference I've found, I'm sure you've heard of Dr Gene Wengert in your 4 years of study;
http://www.thisiscarpentry.com/2010/09/03/moisture-content-wood-movement/

More sources;
https://www.extension.purdue.edu/extmedia/FNR/FNR_403_W.pdf
http://www.woodweb.com/knowledge_base_images/zp/equilibrium_moisture_content.pdf
https://research.cnr.ncsu.edu/blogs...isture-Content-of-Exterior-Wood-in-the-US.pdf

This arm chair quarterback is open to learning.
 
Well you've already changed your statement. In your first statement you said;
"Kiln dried lumber has a moisture content of about 6%. The cell walls undergo a physical and miner chemical chamge due to the forced heat. This change in the cell wall blocks any future absorption of moisture from surrounding humidity."
In the statement above you say;
"There is a cellular change that occurs when kiln drying lumber there by limiting the uptake of moisture"

So, does kiln drying block or just limit moisture uptake, there is a BIG difference between those two statements. If it just limits moisture uptake than my response to you about EMC was correct, it's just kiln dried takes longer to pick up moisture, but it still picks it up.

So from your first statement I'd love to see the evidence of the following-
-That air dried lumber can never get below 10-12%.
-That that Kiln dried lumber will not increase in moisture content, or MC.

Here is a very sound reference I've found, I'm sure you've heard of Dr Gene Wengert in your 4 years of study;
http://www.thisiscarpentry.com/2010/09/03/moisture-content-wood-movement/

More sources;
https://www.extension.purdue.edu/extmedia/FNR/FNR_403_W.pdf
http://www.woodweb.com/knowledge_base_images/zp/equilibrium_moisture_content.pdf
https://research.cnr.ncsu.edu/blogs...isture-Content-of-Exterior-Wood-in-the-US.pdf

This arm chair quarterback is open to learning.
Obviously I am not going to change your "opinion". I attempted to educate the difference which is significant and on a cellular level. If you wish not to believe proven science then that is your right. I will not debate you further. You stated in your first post that you believed others may have more information; however your ego fails to let you hear and understand. Keep doing what you do but please do not spread bad information on a topic you obviously to not totally understand. You have proven once again that the forums are full of misinformation.

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